In the previous chapter, Thomas showed that God does not exist bodily according to His essence (the Incarnation is a separate concern). And then he says, perhaps surprisingly,

This leads to the question of God’s infinity.

We think of a body as the physical part of a human being or animal. In Aristotelian terms, though, a body is any material thing that takes up space: a stone, an apple, a dog, a person. And because it takes up space it is bounded, it has an extent. To put it another way, it’s part of the nature of a body to take up this space rather than that space. And since God is not a body, nor is He a participation in a body, He is not not bounded in this way; He is infinite.

But that word infinite is (it’s tempting to say) infinitely misleading. It’s extremely difficult for anyone who’s taken any kind of higher math not to take this in the mathematical sense, as the sense of counting numbers is infinite; but Thomas means something quite different:

God is not infinite by way of privation, according to which infinity is a passion of quantity; in this sense whatever lacks limits, but is nevertheless capable of having limits by reason of its genus, is said to be infinite.

The counting numbers are infinite; but any given number is finite. Numbers are infinite in the abstract, not in the concrete. But God is infinite in a different way:

Rather, God is infinite negatively, in the sense that a being that is unlimited in every way is infinite.

God is infinite in that His essence includes no notion of limit. He is pure Act, pure Existence, Being itself, not Being as limited to this form or that form (an apple or a dog) but Being precisely as unlimited.

This is a difficult notion to get one’s head around, and in fact, we can only do so negatively. We know what it means for something to be naturally limited, and we say with Hnohra of the Hrossa, “He is not that sort, that he has to live anywhere.”⁠1

Thomas, of course, is more precise:

No act is found to be limited except by a potency that is receptive of the act; thus we observe that forms are limited in accordance with the potency of matter.

A thing that exists exists in actuality; as Thomas would say, it is “in act”. It came to be by actualizing a potency, as the ripe apple comes to be from the green apple by the processing of ripening. But the process of ripening is limited by the apple’s potency to ripen.

Hence, if the first mover is an act without any admixture of potency, as not being the form of any body or a force inhering in a body, it must be infinite.

But of course, the first mover is act without potency, as Thomas showed long since; and so it must be unlimited.

Now follows an illustration that’s worth pondering, just as an instance of how Thomas thinks; but it’s clearly meant to be an example rather than an argument…which is fortunate.

The very order perceived in things is a proof of this. The higher the position occupied in the scale of being, the greater are things found to be in their own way. Among the elements, nobler things are found to be greater in quantity, as also in simplicity. Their generation demonstrates this: as the proportion of the respective elements is increased, fire is generated from air, air from water, and water from earth. And a heavenly body clearly exceeds the total quantity of the elements. Necessarily, therefore, that which is the first among beings and which has nothing above it, must in its own fashion be of infinite quantity.

Thomas’ second illustration is far more interesting:

Nor is there anything to wonder at if what is simple and lacks corporeal quantity is said to be infinite and to exceed in its immensity all quantity of body. For our own intellect, which is incorporeal and simple, exceeds the quantity of all bodies in virtue of its knowledge, and embraces all things. Much more, then, that which is the very first of all exceeds the universe of beings in its immensity, and embraces them all.

According to both Thomas and Aristotle, man’s intellect is immaterial and incorporeal, an aspect of man’s soul that works with man’s body but is not of it. I do not intend to defend that here; but consider that you can think of anything in the universe, and turn it over in your head. Your mind in its simplicity can in some sense encompass all things. How much more so, then, shall God do so?
____1 C.S. Lewis, Out of the Silent Planet, pg 82.